Only apply do_not_use_nightly_on_ci on regular PRs (pytorch#8057)

* Skip do_not_use_nightly_on_ci on release branch

* Only apply do_not_use_nightly_on_ci for regular PRs

* Fix typo

Author: huydhn

.ci/scripts/setup-linux.sh

@@ -23,4 +23,7 @@ fi
 # of nightly. This allows CI to test against latest commits from PyTorch
 install_executorch "use-pt-pinned-commit"
 build_executorch_runner "${BUILD_TOOL}"
-do_not_use_nightly_on_ci
+
+if [[ "${GITHUB_BASE_REF:-}" == *main* || "${GITHUB_BASE_REF:-}" == *gh* ]]; then
+  do_not_use_nightly_on_ci
+fi

.ci/scripts/setup-macos.sh

@@ -137,4 +137,7 @@ install_pytorch_and_domains
 # the pinned commit from PyTorch
 install_executorch "use-pt-pinned-commit"
 build_executorch_runner "${BUILD_TOOL}"
-do_not_use_nightly_on_ci
+
+if [[ "${GITHUB_BASE_REF:-}" == *main* || "${GITHUB_BASE_REF:-}" == *gh* ]]; then
+  do_not_use_nightly_on_ci
+fi